Rotary combustion engine ignition

ABSTRACT

In a preferred embodiment, a rotary combustion engine of the eccentric rotor type includes a housing mounted spark plug which coacts with a plurality of rotor mounted electrodes to provide improved spark ignition for the various combustion chambers of the engine. The rotor mounted electrodes are suitably profiled to optimize the initial spark gap for best spark forming characteristics under various operating conditions.

United States Patent [1 1 Burley et al.

[ ROTARY COMBUSTION ENGINE IGNITION [75] Inventors: Harvey A. Burley, Warren; Carl E.

Bleil, Birmingham; Edward A. Rishavy, Warren; James II. Currie, Rochester, all of Mich.

[731 Assignee: General Motors Corporation,

Detroit, Mich.

[221 Filed: Apr. 15, 1971 [21] Appl. No.: 134,303

[52] US. CL... 123/8.09, 123/169 EL, 123/169 MG [51] Int. Cl. F02b 53/10, F02p 1/00 [58] Field of Search 123/169 MG, 169 EL,

[56] References Cited UNITED STATES PATENTS 10/1967 Horan 123/169 5/1969 Horan 123/169 June 19, 1973 1,461,300 7/1923 Winchester 123/169 3,297,005 1/1967 Lamm l23/8.09 3,288,120 11/1966 Lamm 123/809 FOREIGN PATENTS OR APPLICATIONS 533,145 11/1954 Belgium 123/169 Primary Examiner-Laurence M. Goodridge Assistant Examiner-Ronald B. Cox Att0rney.l. L. Carpenter and Robert J. Outland [57] ABSTRACT In a preferred embodiment, a rotary combustion engine of the eccentric rotor type includes a housing mounted spark plug which coacts with a plurality of rotor mounted electrodes to provide improved spark ignition for the various combustion chambers of the engine. The rotor mounted electrodes are suitably profiled to optimize the initial spark gap for best spark forming characteristics under various operating conditions.

1 Claim, 4 Drawing Figures Patented June 19, 1973 3,739,753

,2 Shuts-Sheet I 1 INVENT RS Haz'r ABarBey, Car! .B/eii 'dzaardfljzz'slmxy & fzmes Hl Carrie ATTORNEY 1 ROTARY COMBUSTION ENGINE IGNITION BACKGROUND OF THE INVENTION This invention relates to rotary internal combustion engines and, more particularly, to improved ignition means for use in conjunction with such engines and especially in rotary engines of the eccentric rotor type.

Numerous constructions of rotary internal combustion engines have been proposed in whicha rotor turns either concentrically or eccentrically within a housing having an internal peripheral wall. swept by seals carried by the rotor. Of particular current interest in this field are engines of the eccentric rotor type in which the rotor is eccentrically rotatable and acts as a piston dividing a multi-lobed cavity into a plurality of rotating working chambers. The working chambers are each associated with one side of the multi-sided rotor and are separated by seals carried in the apexes and along the ends of the rotor.

In engines of this type ignition of the compressed charge has commonly been accomplished through means of one or two housing carried sparkplugs having their electrodes located within recessed openings in the peripheral wall. The passage of the rotor seals over this wall prevents the spark plug electrodes from-protruding into the open portion of the combustionchamber, as is conventional in reciprocating piston type engines and thus, ignition of the charge has required that suitable amounts of the combustible mixture be swept into the recessed openings in whichthe spark plugs are located.

SUMMARY OF THE INVENTION The present invention. provides improved ignition means for use in conjunction with rotary combustion engines, especially those of the eccentric rotor type. These improved ignition means include a housing mounted spark plug having a single electrode, which cooperates with a plurality of rotor mounted electrodes to provide ignition sparks that transverse open portions of the respective engine working chambers as they reach their desired ignition points.

An advantage of the invention is that the igntion spark is brought more intimately into contact with the main body of combustible mixture, resulting in more positive ignition under a wider range of operating conditions. In view of this improvement, it is anticipated that a single spark plug may be used where, in the past, two have been required to obtain satisfactory operation. However, if desired, the use of a plurality of spark plugs is possible within the scope of the present invention in order to obtain even more advantageous operating conditions.

The present invention further provides for the contouring of the surfaces of the various rotor mounted electrodes in order to provide for suitably varying the BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a transverse cross-sectional view of a rotating internal combustion engine, including ignition means in accordance with the invention;

FIG. 2 is an enlarged cross-sectional view of a portion of the engine of FIG. 1, showing details of the rotor and housing mounted electrodes, as located in one of the desired spark creating positions;

FIG. 3 is a fragmentary plan view of the engine rotor taken generally in the plane indicated by the line 3-3 of FIG. 2 and showing one of the combustion recesses and its rotor mounted electrode; and

FIG. 4 is a graphical illustration of how the combination of varying the spark timing and profiling the rotor mounted electrode may be utilized to affect the time and length of spark travel under various engine operating conditions.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, numeral 10 generally indicates a rotary combustion engine of the known eccentric rotor type. Engine 10 includes a housing 12 which encloses an internal cavity 14. Cavity 14 is defined by an inwardly facing peripheral wall 16 which is preferably of substantially trochoidal configuration, and by a pair of end walls 18, only one being shown.

Wthin cavity 14 there is disclosed a generally triangular rotor 20 which is mounted for rotation on an eccentric portion 22 of a shaft that extends longitudinally through the cavity 14. Rotor 20 includes three equally spaced generally convex sides or faces 24 which face the peripheral wall 16 and cooperate therewith to define three variable volume combustion or working chambers 26. Apex seals 28 and side seals 30 are provided at the corners and on the ends of the rotor, respectively, to seal the various working chambers against excessive leakage of gases from one chamber to another.

Engine 10 is conventionally provided with an inlet port 32 which opens to cavity 14 through an end wall 18 and connects the cavity with an external inlet fitting or manifold 34. Preferably the engine is provided with dual ports 32 which open at oppositely disposed locations of the two opposing end walls 18 and are both connected with the manifold 34. The engine also includes an exhaust port 36 which opens through peripheral wall 16 to the cavity 14 and connects it with an exhaust fitting or manifold 38.

The foregoing description discloses conventional portions of a known type of rotary internal combustion engine, as to which further description is not believed necessary. The present invention differs from the prior art arrangements in the manner of constructing the ignition system for the engine.

The ignition system includes a distributor 40 which is connected in conventional manner with a source of electric voltage, not shown. Distributor 40 is electrically connected to a modified spark plug 42 which is secured in a threaded opening 44. Opening 44 is preferably located to connect with cavity 14 at a point on the peripheral wall 16 midway between the end walls 18 and approximately at the narrow waist portion of the epitrochoidal cavity that is generally opposite the side on which the inlet and outlet ports 32, 36 are located. Spark plug 42 ineludesa singlecentral electrode 46 which is insulated from the threaded body 48 and extends inward to a point substantially flush with but not inwardly of the inner surface of the peripheral wall 16.

Centered in each of the three working faces 24 of the triangular rotor is a recessed transfer passage 50 that provides for the transfer of working gases across the narrow central portion of the peripheral wall, where it is closely approached by the sides of the rotor. Within each of these transfer passages 50 and located approximately centrally of the respective rotor faces 24 is a radially extending electrode 52, preferably formed as an integral portion of the rotor 20.

Electrodes 52 are arranged so that they pass in close proximity to the central spark plug electrode 46 when their respective combustion chambers 26 are at about the desired location for ignition of the fuel-air charge. This occurs when the respective chambers are near their smallest volumes, when the respective rotor faces are almost directly facing the narrowed portion of the peripheral wall which contains the spark plug.

It should be noted that suitable electrical paths to complete the circuit from the rotor to ground and thence back to the voltage source are provided by the bearings supporting the rotor and its shaft, as well as by the rotor gear teeth 54 which engage a housing carried gear, not shown, to properly control rotation of the rotor. If desired, however, additional means could be provided to complete the electrical circuit.

Preferably, though not necessarily, rotor mounted electrodes 52 are relatively narrow in a direction axi ally of the rotor, having a width not substantially more than the thickness of the spark plug electrode 46. Electrodes 52 are, however, of sufficient dimension in a direction circumferentially of the rotor to provide for satisfactory ignition and duration of a spark between the spark plug and rotor mounted electrodes 52 under all the various conditions of engine speed and spark timing which may be desired.

To provide desirable characteristics of the ignition spark under various operating conditions of the engine, it is proposed that the outer surfaces of electrodes 52 be profiled so as to provide predetermined differing spark gaps at various points of the rotor movement. As best shown, for example by FIG. 4, the rotor mounted electrodes of the disclosed arrangement are profiled to provide four distinct spark gap differences at separate areas A, B, C and D, which in nonnal rotation of the rotor pass sequentially by spark plug electrode 46. In this instance, the spark gaps provided between the spark plug electrode and the various areas of the rotor mounted electrodes are as follows:

0.100 inches for the initial area A;

0.050 inches for the secondary area B;

0.025 inches for the central area C; and

0.100 inches for the terminal area D.

FIG. 4 also indicates that the circumferential extent of the rotor mounted electrodes 52 is equal to a rotor movement of and a rotor shaft rotation of 45, in either direction from the dead center position of smallest combustion chamber volume.

In operation, eccentric rotation of the rotor in a counterclockwise direction, as shown in the drawings, causes a combustible mixture to be drawn in through the inlet ports 32 and carried with the respective combustion chambers through the conventional cyclic events of intake, compression, combustion, expansion and exhaust. As each combustion chamber approaches its dead center smallest volume opposite the spark plug 42, the rotor carried electrode 52 for that chamber passes adjacent the central electrode 46 of the spark plug with a predetermined gap, as previously indicated. At a predetermined time in the cycle, the distributor connects the ignition system to impress a voltage across the opposed electrodes 46, 52, causing a spark to jump between them. Once initiated, the spark continues until the energy charge in the ignition system is dissipated in a manner which is common among gasoline type internal combustion engines. Preferably, the timing of the initial spark is varied in a conventional manner in response to the speed and load conditions of the engine, so that the spark timing is advanced as the engine speed increases and also is advanced by increased vacuum in the intake manifold.

In a typical ignition system, the spark burns for about one millisecond under heavy loads and about 1.5 milliseconds under light loads such as deceleration. With this in mind, there is indicated in FIG. 4 the burn time for various engine conditions with respect to the position of the rotor mounted electrode.

It can be seen that during starting and wide open throttle, when the load is high, the spark is initiated in area C, where the gap is smallest. At high engine speeds, the spark gap is opened up slightly during the burn time, but this will not extinguish the arc. Typical cruise conditions will result in the spark being initiated in area B, where the spark gap is about 0.050 inches. In closed throttle deceleration with high vacuum (designated NPS in FIG. 4) the spark is initiated in area A, where the gap is 0.100 inches. Alternatively, the vacuum advance mechanism may be arranged with the socalled ported spark, (PS in the figure) in which the vacuum advance device is vented to atmosphere during closed throttle deceleration. In this case, the spark will be initiated in area C but will continue to burn well into area A, where the gap reaches 0.100 inches. At light loads in second and third gears the spark would be initiated in area B with a gap of 0.050 inches.

In this manner, profiling of the rotor mounted electrode may be utilized to provide optimum spark gap size for igniting the fuel-air mixture under the various operating conditions which may be encountered in an engine.

The preferred arrangement of this invention is believed to have a number of significant advantages over the presently known ignition systems for rotary combustion engines:

1. Two recessed spark plug ports are eliminated and therefore the quantity of unburned hydrocarbons trapped in the quench zones and crevices is reduced.

2. Only one spark plug and ignition system per rotor is required, instead of two.

3. With one less spark plug to accommodate in the housing, there is room for additional cooling passages which provides design advantages. For example, the use of cast iron rather than the usual aluminum for a housing material would be made easier.

4. Ignition of the fuel-air mixture is improved because the spark occurs out in the mixture instead of in recessed openings.

5. Ignition of lean mixtures at light engine loads is improved because of the greater spark gap length possible due to profiling of the rotor mounted electrodes.

6. Reduced spark plug fouling is encountered, due to the scrubbing action of the fuel-air mixture on the spark plug insulator and to the higher peak insulator temperatures.

While the invention has been described by reference to a preferred embodiment, it is to be understood that numerous changes could be made within the scope of the inventive concepts disclosed and, accordingly, the invention is not intended to be limited except by the language of the following claims.

We claim: 7

l. A rotary internal combustion engine having a housing with an internal rotor defining with said housing a plurality of variable volume working chambers,

a primary'electrode mounted in said housing and exposed to said chambers,

a plurality of secondary electrodes on said rotor, one

in each of said chambers,

said primary and secondary electrodes being positioned such that the outer surface of the secondary electrode of each working chamber. passes in closely opposed relation to said primary electrode when said working chamber is near its position of smallest volume, and

means adapted to create and momentarily maintain an electric are between the primary electrode and each of the secondary electrodes during various portions of the movement of said electrodes in opposed relation, said arc being of intensity sufficient to ignite a combustible fuel-air mixture in the respective working chamber,

said secondary electrodes each having their outer surfaces profiled to form a plurality of adjacent, circumferentially spaced areas arranged in steplike fashion, said adjacent areas being positioned at difi'ering levels to provide a predetermined variation of clearance between the primary electrode and the adjacent areas of the secondary electrode as they pass sequentially opposite the primary electrode so as to vary in a desired manner the length and intensity of arcs initiated and maintained between said electrodes during said various portions of their movement in opposed relation. 

1. A rotary internal combustion engine having a housing with an internal rotor defining with said housing a plurality of variable volume working chambers, a primary electrode mounted in said housing and exposed to said chambers, a plurality of secondary electrodes on said rotor, one in each of said chambers, said primary and secondary electrodes being positioned such that the outer surface of the secondary electrode of each working chamber passes in closely opposed relation to said primary electrode when said working chamber is near its position of smallest volume, and means adapted to create and momentarily maintain an electric arc between the primary electrode and each of the secondary electrodes during various portions of the movement of said electrodes in opposed relation, said arc being of intensity sufficient to ignite a combustible fuel-air mixture in the respective working chamber, said secondary electrodes each having their outer surfaces profiled to form a plurality of adjacent, circumferentially spaced areas arranged in sTep-like fashion, said adjacent areas being positioned at differing levels to provide a predetermined variation of clearance between the primary electrode and the adjacent areas of the secondary electrode as they pass sequentially opposite the primary electrode so as to vary in a desired manner the length and intensity of arcs initiated and maintained between said electrodes during said various portions of their movement in opposed relation. 